In many electrical applications, it is desirable to connect an electrical component with or without conductive terminals leads extending therefrom, to a substrate including a plurality of laterally spaced conductive paths. A current is passed between the aligned conductor contact of the electrical component to the substrate path. It is undesirable for current to pass between the electrical contacts causing shorting of the circuit.
Conventional methods have connected electrical components which include conductive terminals leads extending therefrom by soldering techniques. It is also known to use a uniaxial conductive adhesive resin for mounting electrical components having terminals extending therefrom, as disclosed in U.S. Pat. No. 4,667,401 issued May 26, 1987 in the name of Clements et al., common inventor to the subject application. The patent discloses a uniaxial conductive adhesive wherein pressure between two members causes conductivity therebetween by concentration of conductive metal particles within the resin, while the areas surrounding the depressed members remain non-conductive.
U.S. Pat. No. 4,113,981 to Fujita et al., issued Sep. 12, 1978 discloses an electrically conductive adhesive for connecting raised conductors or terminals of electronic devices. Pairs of connecting terminals are attached to plates such that the connecting terminals project from the surface of the plates. Upon pressure of the plates to one another, the terminal compressed the resin to obtain conductivity between metal particles within a resin. Portions between the plates absent the terminals are not conductive due to the left compression thereof as being recessed from the connecting terminals.
U.S. Pat. No. 4,640,981 issued Feb. 3, 1987 in the name of Dery et al. discloses electrical interconnection means which utilizes two members having printed thereon ink conductors. The members were placed facing one another with an adhesive therebetween. In order to obtain conductivity between the two members, pressure is applied to an area of one of the members to bring the conductive inks into contact with each other forcing the flow of adhesive therefrom.
It is known in the art to deposit layers to the conductive portions on the electrical contacts of the electrical component utilizing several plating steps, i.e. sputtering which is generally very expensive and time consuming. U.S. Pat. No. 4,811,081 issued Mar. 7, 1989 in the name of Lyden discloses use of an anisotropically electrically conductive adhesive which is used between a projecting contact pad and conductive path on a substrate.
However, this prior art is inapplicable to electrical components which do not have terminal leads or "bumps" extending therefrom. In general, these type of components include the passivating layer which is discontinuous exposing recessed areas of electrical contact pads. The passivating layer may have a thickness of 0.3-0.9 microns and is very fragile. The layer can not take the pressure of the prior art and isotropic adhesives. The above methods do not apply to this type of an electrical component due to the electrical contacts being recessed rather than extending therefrom allowing pressure directly thereon.
U.S. Pat. No. 4,423,435 issued Dec. 27, 1983 in the name of Test, II discloses use of an anisotropically electrically conductive adhesive solvent which is placed between contact pads and conductive paths of a substrate. As the solvent evaporates, the resin will contact predominantly along the Z axis remaining non-conductive along the X- and Y-axes. The resin is heated to activate the adhesive.